1. Field of Invention
The present invention relates to an LED light source device, and more specifically, an LED light source device in which light from an LED (Light-Emitting Diode) is emitted in a specified direction and within a certain range via an optical member.
2. Description of Related Art
Conventionally, luminescent elements (LEDs) are used as a light source, an optical member is used such as a lens so that the light from this light source is radiated in a specific direction, and an LED light source device is widely used in order to control the light distribution from this optical member. (For an example, refer to published Japanese Patent Application No. H08 (1996)-107235.)
In order to effectively make use of light from luminescent elements (LEDs) used as a light source in an LED light source device of this constitution, a configuration is presented whereby a reflecting mirror is provided in order to cause the portion of light from the luminescent elements that does not reach the optical member to be guided toward it. (For an example, published Japanese Patent Application No. 2004-281605 (U.S. Pat. No. 7,111,964 B2).)
Specifically, FIG. 11 shows an LED light source device as disclosed in published Japanese Patent Application No. 2004-281605 (U.S. Pat. No. 7,111,964 B2). This device is provided with luminescent elements (LEDs) 21 as a light source along with a reflecting mirror 108 which has a reflecting surface 108A composed of an aluminum vapor deposition film. Further, the optical member 103 is composed of the following: a first optical part 104 in which a translucent resin is used as a substrate 101, onto which the luminescent elements (LED) 21 are provided, and the light from these elements is refracted and radiated in a direction perpendicular to the Z-axis direction; a second optical part 105 in which the light from the luminescent elements 21 is condensed and radiated in the Z-axis direction; and a third optical part 106 in which the light from the luminescent elements 21 is radiated in the Z-axis direction based on its total reflection.
With the optical member 103 of this LED light source device, based on the first optical part 104, the light in the 60-90° range direction from the aperture half-angle of the luminescent elements 21 (that is, the angle with respect to the center axis of the luminescent elements 21, or the Z-axis in FIG. 11) as a portion of the light from the luminescent elements 21 is refracted and radiated in a direction perpendicular to the Z-axis direction. Based on the second optical part 105, the light in the 35° or less range direction from the aperture half-angle of the luminescent elements 21 as a portion of the light from the luminescent elements 21 is radiated in the Z-axis direction. And based on the third optical part 106, the light in the 35-60° range direction from the aperture half-angle of the luminescent elements 21 undergoes total reflection and is radiated in the Z-axis direction.
In FIG. 11, element 101 is a substrate in which an insulation layer 101B is deposited onto the base material 101A, and a wiring pattern 101C is formed on this insulation layer 101B. Further, in this figure, element 107 is a wire, L5 is a pathway for the light that first enters the second optical part 105 and is then radiated from the hemispherical light radiation surface 105A, L6 is a pathway for the light that first enters the third optical part 106 and is then reflected by the reflection surface 106B and radiated from the disk-shaped light radiation surface 106A, and L7 is a pathway for the light that first enters and exits the first optical part 104 and is then reflected by the reflecting mirror 108.
Based on an LED light source device of this configuration, it is possible to control the majority of light from luminescent elements 21 using the optical member 103, which is to say that it becomes possible to reduce the amount of light that is guided to the optical member 103 through the action of the reflecting mirror 108. Accordingly, it becomes unnecessary to install a large reflecting mirror, and by installing this reflecting mirror 108 the need for a large-scale device can be prevented, thus making it possible to design a small-scale LED light source device.
However, with this type of LED light source device, light that is reflected by the reflecting mirror 108 and then radiated (specifically, light that is radiated by passing through the first optical part 104) passes through multiple boundary surfaces (specifically, for example, the boundary surface between the optical member 103 and the air layer that exists along the periphery of this optical member 103) in order to be radiated, and therefore, there is a large rate of occurrence of boundary reflection and reflection loss caused by refraction, etc., that occurs at these boundary surfaces. As a result, a high factor of light utilization cannot be achieved. Moreover, for the sake of achieving a favorable form of radiated light, it is necessary to create designs that take into consideration these instances of refraction at the boundary surfaces, and the problem is that such designs themselves are difficult to produce.
Furthermore, in this LED light source device, a reflecting mirror 108 is provided for the purpose of making use of high-angle light (for example, light with a range direction in which the aperture half-angle of the luminescent elements 21 exceeds 60°), but in the case of this high-angle light, the level of light is lower compared to that of low-angle light. For this reason, on a surface that has been irradiated by the light from this LED light source device, the illuminance in the peripheral area in which light that is reflected by the reflecting mirror 108 is irradiated is considerably lower when compared to the illuminance in the center area. Because of this, a problem exists in which it is difficult for irradiation to be conducted in a uniform manner on this irradiated surface at a high illuminance. Therefore, this type of LED light source device is not suitable for light irradiation of surfaces that have a considerable amount of surface area. That is to say, in order to provide light irradiation on a surface that has a broad surface area, several LED packages composed of luminescent elements and optical members must be provided, and even in cases where the configuration is such that these multiple LED packages are arranged on a common substrate, it is impossible to conduct even irradiation of light onto the surface, and moreover, it is impossible to obtain a sufficient illuminance in order to do so.